Method for keeping mobile initiated connection only mode user equipment in connected mode

ABSTRACT

The present disclosure relates to a communication technique for converging an IoT technology with a 5G communication system for supporting a higher data transfer rate beyond a 4G system, and a system therefor. The present disclosure can be applied to an intelligent service (e.g. a smart home, a smart building, a smart city, a smart car or connected car, healthcare, digital education, a retail business, a security and safety-related service, etc.) on the basis of a 5G communication technology and an IoT-related technology. The present disclosure provides a method wherein, after a MICO mode terminal establishes a connection and transmits data, the MICO mode terminal can be kept in a connected mode state, rather than entering an idle mode, in order to provide for a case where slightly delayed response traffic occurs according to the type of application or service.

TECHNICAL FIELD

In the detailed description of embodiments of the disclosure, a radioaccess network will be mainly discussed on the basis of the 5G networkstandard defined by 3GPP, including a new RAN (NR) corresponding to acore network, and a packet core (5G system, 5G core network, or NG core(next-generation core)), but the main subject of the disclosure can beapplied with a slight change to other communication systems having asimilar technical background within the range that does not depart fromthe scope of the disclosure by the determination of a person skilled inthe art.

For the convenience of description, the disclosure uses terms and namesdefined in the 3^(rd)-generation partnership project long-term evolution(3GPP LTE). However, the disclosure is not limited to the terms andnames, and may be equally applied to a system following anotherstandard.

A UE according to an embodiment of the disclosure may be specialized asan Internet of Things (IoT) UE and may be useful as a UE having afunction of communication with low power.

BACKGROUND ART

In order to meet wireless data traffic demands, which have increasedsince the commercialization of a 4G communication system, efforts todevelop an improved 5G communication system or a pre-5G communicationsystem have been made. For this reason, the 5G communication system orthe pre-5G communication system is called a beyond-4G-networkcommunication system or a post-LTE system. In order to achieve a highdata transmission rate, implementation of the 5G communication system ina mmWave band (for example, a 60 GHz band) is being considered. In the5G communication system, technologies such as beamforming, massive MIMO,full-dimensional MIMO (FD-MIMO), array antenna, analog beamforming, andlarge-scale antenna techniques are being discussed as means to mitigatea propagation path loss in the mmWave band and increase a propagationtransmission distance. Further, for use in the 5G communication system,technologies such as an evolved small cell, an advanced small cell, acloud Radio Access Network (RAN), an ultra-dense network,device-to-device communication (D2D), a wireless backhaul, a movingnetwork, cooperative communication, Coordinated Multi-Points (CoMP), andreceived interference cancellation have been developed to improve thesystem network. In addition, for use in the 5G system, advanced codingmodulation (ACM) schemes such as hybrid FSK and QAM modulation (FQAM)and sliding window superposition coding (SWSC), and advanced accesstechnologies such as filter bank multi carrier (FBMC), non-orthogonalmultiple access (NOMA), and sparse code multiple access (SCMA) have beendeveloped.

Meanwhile, the Internet has evolved from a human-oriented connectionnetwork in which humans generate and consume information to the Internetof Things (IoT), in which distributed components such as objectsexchange and process information. Internet-of-everything (IoE)technology, in which a big-data processing technology is combined withthe IoT technology through connection via a cloud server or the like,has emerged. In order to implement the IoT, technical factors such as asensing technique, wired/wireless communication, network infrastructure,service-interface technology, and security technology are required, andresearch on technologies such as a sensor network, machine-to-machine(M2M) communication, machine-type communication (MTC), and the like forconnection between objects has recently been conducted. In an IoTenvironment, through collection and analysis of data generated inconnected objects, intelligent Internet technology (IT) service thatcreates new value in peoples' lives may be provided. The IoT may beapplied to fields such as those of a smart home, a smart building, asmart city, a smart car, a connected car, a smart grid, health care, asmart home appliance, or high-tech medical services through theconvergence of the conventional Information technology (IT) and variousindustries.

Accordingly, various attempts to apply 5G communication to the IoTnetwork are being made. For example, 5G communication technologies suchas a sensor network, machine-to-machine (M2M) communication, andmachine-type communication (MTC) are being implemented usingbeamforming, MIMO, and array antenna schemes. The application of a cloudRAN as big-data processing technology may be an example of convergenceof the 5G technology and the IoT technology.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

MICO is the abbreviation for “mobile initiated communication only”, anda MICO-mode UE is a UE having a connection with a network only when theUE has data to be transmitted. In other words, if the MICO-mode UE is inan idle state, the MICO-mode UE does not receive paging. Accordingly,the network cannot wake up the MICO-mode UE in the idle state and maydetermine that the corresponding UE is reachable only when the MICO-modeUE wakes up and makes a request for connection to the network. Forexample, if an SMS server is congested, a time delay may occur when aresponse SMS is transmitted in response to an SMS message transmitted bythe UE. If the UE returns to the idle mode during the delay time, thenetwork cannot wake up the MICO-mode UE to transmit the response SMS.

Accordingly, the disclosure provides a method of preventing theMICO-mode UE from entering the idle mode so as to remain in theconnected mode in the event where response traffic is somewhat delayeddepending on the type of application or the type of service after theMICO-mode UE establishes the connection and transmits data. Further, thedisclosure broadly provides a method by which, if an application serverdesires to transmit planned traffic at a specific time, the network maycontrol the MICO-mode UE to remain in the connected mode until thecorresponding time.

A mobility restriction area is a set of area information including anallowed area in which a session is capable of being establishedaccording to the location of the UE and thus data can be exchanged, anon-allowed area in which a session for data communication cannot beestablished but only control signaling is possible, and a forbidden areain which no mobile communication services are possible.

Accordingly, the disclosure proposes an operation of paging the UE whenthe UE is in a non-allowed area and a method of processing a sessionmanagement message that the UE transmits along with a registrationrequest when allocating and managing the mobility restriction area forcontrolling service according to movement of the UE. A 5G network shouldbe able to determine when to page the UE in the non-allowed area.Further, if the UE transmits a message for establishing a session to theAMF in the state in which the UE is not aware that the UE is present inthe non-allowed area, the AMF should be able to determine how to processthe message. Through the disclosure, it is not possible for the UE touse the session in the non-allowed area, but the session may beestablished in advance within the network and may be activated when theUE moves to an allowed area.

Solution to Problem

In accordance with an aspect of the disclosure, a method of performingcommunication by a base station in a wireless communication system isprovided. The method includes: receiving, from an access and mobilitymanagement function (AMF), a first message including information formaintaining a mobile initiated communication only (MICO) mode terminalin a connected state; determining whether to release the connection ofthe MICO mode terminal based on the information; and in case that it isdetermined to release the connection of the MICO mode terminal,transmitting, to the AMF, a second message making a request forreleasing the connection.

The determining of whether to release the connection may include:configuring a timer for a connection maintenance time of the MICO modeterminal based on the information; and in case that the timer expires,determining to release the connection of the MICO mode terminal.

The information may include at least one piece of information indicatingthat the UE is using a MICO mode and information on the time for whichthe UE should maintain the connected state in the MICO mode.

The determining of whether to release the connection may includeconfiguring a larger value between a radio resource control (RRC)inactive timer and the time for which the UE should maintain theconnected state in the MICO mode as a timer for a connection maintenancetime of the MICO mode terminal and determining whether the timerexpires.

The first message may be a message for installing context of the UE inthe base station or establishing a data radio bearer.

The method may further include releasing radio resources and a beareraccording to a determination to accept the release of the connection ofthe MICO mode terminal by the AMF.

In accordance with another aspect of the disclosure, a method ofperforming communication by an access and mobility management function(AMF) is provided. The method includes: transmitting a first messageincluding information for maintaining a mobile initiated communicationonly (MICO) mode terminal in a connected state to a base station; and incase that it is determined to release the connection of the MICO modeterminal based on the information, receiving a second message making arequest for releasing the connection from the base station.

The receiving of the second message may include, in case that a timerfor a connection maintenance time of the MICO mode terminal configuredbased on the information expires, receiving the second message makingthe request for releasing the connection from the base station.

The method may further include: determining whether to accept therelease of the connection of the MICO mode terminal; and in case that itis determined to accept the release of the connection of the MICO modeterminal, transmitting a third message accepting the release of theconnection of the MICO mode terminal to the base station.

The method may further include: receiving information on a communicationpattern of the MICO mode terminal from an application server; andconfiguring information for maintaining the MICO mode terminal in theconnected state on the basis of the information on the communicationpattern of the MICO mode terminal.

In accordance with another aspect of the disclosure, a base station isprovided. The base station comprises: a transceiver configured totransmit and receive a signal; and a controller configured to receive afirst message including information for maintaining a mobile initiatedcommunication only (MICO) mode terminal in a connected state from anaccess and mobility management function (AMF), determine whether torelease the connection of the MICO mode terminal based on theinformation, and in case that it is determined to release the connectionof the MICO mode terminal, transmit a second message making a requestfor releasing the connection to the AMF.

In accordance with another aspect of the disclosure, an access andmobility management function (AMF) is provided. The AMF comprises: atransceiver configured to transmit and receive a signal; and acontroller configured to transmit a first message including informationfor maintaining a mobile initiated communication only (MICO) modeterminal in a connected state to a base station, and in case that it isdetermined to release the connection of the MICO mode terminal based onthe information, receive a second message making a request for releasingthe connection from the base station.

Advantageous Effects of Invention

According to an embodiment of the disclosure, a mobile communicationservice provider can effectively support a UE having delayed traffictransmission for each service used by the UE or according to a requestfrom an application server that provides a service to the UE. TheMICO-mode UE is suitable for a UE requiring low-power communication, andas a result, is connected to a network and communicates only when the UEhas data to be transmitted. However, when the corresponding UE transmitsresponse traffic in response to traffic transmitted by the UE, somewhatdelayed traffic transmission may occur according to a service or a stateof the application server. For example, if an SMS server is congested, atime delay may occur when a response SMS is transmitted in response toan SMS message that the UE transmitted. If the UE returns to the idlemode during the delay time, the network cannot wake up the MICO modeterminal to transmit the response SMS thereto. Accordingly, the presentembodiment provides an effect in that a data communication service canbe provided without loss of traffic transmitted to the UE since thenetwork can maintain the MICO mode terminal in the connected state for aspecific time with respect to a service or traffic expected to bedelayed.

According to an embodiment of the disclosure, when the 5G networkperforms paging in the non-allowed area, the UE can determine a serviceto be used as a response thereto. Through the disclosure, after making arequest for a PDU session in the non-allowed area, the UE can activateand use the corresponding session when moving to the allowed area. Ittakes a shorter time than the case in which the UE enters the allowedarea and makes a request for establishing a PDU session again to use thesame, and less signaling is generated from the viewpoint of the network.

According to an embodiment of the disclosure, the 5G core network maydetermine to page the UE to use a specific service, for example, anemergency call, an SMS service, a location-tracking service, or a publicsafety service even though the UE is in the non-allowed area. Further,the network side establishes the session and configures a context inadvance in response to a PDU session establishment request message sentby the UE in the non-allowed area, so that it is possible to reduce aPDU session establishment time of the UE and signaling when the UE movesto the allowed area and uses the PDU session.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a procedure in which a 5G core network transmitsinformation for maintaining a MICO mode terminal in a connected state toa RAN;

FIG. 2 illustrates a method by which a 5G core network storesinformation for maintaining a MICO mode terminal in a connected stateand controls the release of a RAN connection;

FIG. 3 illustrates a method by which a 5G core network receives acommunication pattern for a corresponding UE from a 3rd-partyapplication server through an NEF and controls a MICO timer;

FIG. 4 illustrates a method by which a 5G core network receives acommunication pattern for a corresponding UE from a 3rd-partyapplication server through a PCF and controls a MICO timer;

FIG. 5 illustrates a procedure in which a 5G core network performs adetermination to provide a specific service to a UE in a non-allowedarea, a paging method, and a response method of the UE;

FIG. 6 illustrates a method by which a 5G network processes a sessionestablishment request message transmitted by a UE in a non-allowed areaand a method of activating a session by the UE in the future;

FIG. 7 illustrates a method of establishing a connection for a PDUsession between a UE, a 5G RAN, and a UPF according to an embodiment ofthe disclosure;

FIG. 8 is a block diagram illustrating a base station according to anembodiment of the disclosure; and

FIG. 9 is a block diagram illustrating an AMF according to an embodimentof the disclosure.

MODE FOR CARRYING OUT THE INVENTION

In a description of embodiments of the disclosure, a description oftechnologies that are already known to those skilled in the art and arenot directly relevant to the disclosure is omitted. Such an omission ofunnecessary descriptions is intended to prevent obscuring of the mainidea of the disclosure and more clearly transfer the main idea.

For the same reason, in the accompanying drawings, some elements may beexaggerated, omitted, or schematically illustrated. Further, the size ofeach element does not entirely reflect the actual size. In the drawings,identical or corresponding elements are provided with identicalreference numerals.

The advantages and features of the disclosure and ways to achieve themwill be apparent by making reference to embodiments as described belowin detail in conjunction with the accompanying drawings. However, thedisclosure is not limited to the embodiments set forth below, but may beimplemented in various different forms. The following embodiments areprovided only to completely disclose the disclosure and inform thoseskilled in the art of the scope of the disclosure, and the disclosure isdefined only by the scope of the appended claims. Throughout thespecification, the same or like reference numerals designate the same orlike elements.

Here, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions can be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions specified in the flowchart block or blocks.These computer program instructions may also be stored in a computerusable or computer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstruction means that implement the function specified in the flowchartblock or blocks. The computer program instructions may also be loadedonto a computer or other programmable data processing apparatus to causea series of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

And each block of the flowchart illustrations may represent a module,segment, or portion of code, which includes one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

As used herein, the “unit” refers to a software element or a hardwareelement, such as a Field Programmable Gate Array (FPGA) or anApplication Specific Integrated Circuit (ASIC), which performs apredetermined function. However, the “unit does not always have ameaning limited to software or hardware. The “unit” may be constructedeither to be stored in an addressable storage medium or to execute oneor more processors. Therefore, the “unit” includes, for example,software elements, object-oriented software elements, class elements ortask elements, processes, functions, properties, procedures,sub-routines, segments of a program code, drivers, firmware,micro-codes, circuits, data, database, data structures, tables, arrays,and parameters. The elements and functions provided by the “unit” may beeither combined into a smaller number of elements, “unit” or dividedinto a larger number of elements, “unit”. Moreover, the elements and“units” may be implemented to reproduce one or more CPUs within a deviceor a security multimedia card. Also, in an embodiment, the ‘˜ unit’ mayinclude one or more processors.

Embodiment 1

In the detailed description of embodiments of the disclosure, a radioaccess network will be mainly discussed on the basis of the 5G networkstandard defined by 3GPP, including a new RAN (NR) corresponding to acore network, and a packet core (5G system, 5G core network, or NG core(next-generation core)), but the main subject of the disclosure can beapplied with a slight change to other communication systems having asimilar technical background within the range that does not depart fromthe scope of the disclosure by the determination of a person skilled inthe art.

For the convenience of description, the disclosure uses terms and namesdefined in the 3rd-generation partnership project long-term evolution(3GPP LTE). However, the disclosure is not limited to the terms andnames, and may be equally applied to a system following anotherstandard.

Entities in the disclosure will be described below.

A user equipment (UE) is connected to a radio access network (RAN) andaccesses a device that performs a mobility management function of a 5Gcore network device. In the disclosure, the device is called an accessand mobility management function (AMF). This refers to a function or adevice that performs both access to the RAN and mobility management. TheAMF serves to route a session-related message of the UE to a sessionmanagement function (SMF). The AMF is connected to the SMF, and the SMFis connected to a user plane function (UPF), allocate user planeresources to be provided to the UE, and establishes a tunnel fortransmitting data between a base station and the UPF.

MICO is an abbreviation for “mobile initiated communication only”, and aMICO-mode UE is a UE having a connection with a network only when the UEhas data to be transmitted. In other words, if the MICO-mode UE is in anidle state, the MICO-mode UE does not receive paging. Accordingly, thenetwork cannot wake up the MICO-mode UE in the idle state, and maydetermine that the corresponding UE is reachable only when the MICO-modeUE wakes up and makes a request for connection to the network. Forexample, if an SMS server is congested, a time delay may occur when thenetwork transmits a response SMS in response to an SMS message that theUE transmitted. If the UE returns to the idle mode during the delaytime, the network cannot wake up the MICO-mode UE to transmit theresponse SMS. In another example, if there is a characteristic oftolerating a long delay time (delay tolerance), which is one of thecharacteristics of IoT traffic, an IoT UE using a MICO mode transmitstraffic, and if the UE returns to the idle mode while waiting for aresponse thereto, delayed response traffic, which an application servertransmits, cannot be transmitted to the UE. Accordingly, the disclosureproposes a method of providing an appropriate data traffic service bymaintaining the MICO-mode UE in a connected state for a predeterminedtime in a 5G core network. In another example, the application servermay set a communication pattern of a specific UE through a networkexposure function (NEF). For example, a service provided to a specificUE may have a delayed communication characteristic, or the time forwhich the specific UE performs data communication and the time taken fordata communication to be performed once may be transmitted to the 5Gcore network. After receiving the information, the AMF may use theinformation to maintain the connected state of the MICO-mode UE. If thetime at which the UE wakes up is close to the time at which the UEshould perform data communication, the AMF may maintain the UE in theconnected state. If the UE wakes up and receives a value indicating datacommunication for 1 minute, the corresponding UE may be maintained inthe connected state for 1 minute.

The disclosure describes data transmission by way of example, but aservice such as an SMS may be included as one example of datatransmission. Alternatively, a service of transmitting and receivingdata may be included in order to detect location information of the UE.

Embodiment 1-1 and FIG. 1

FIG. 1 illustrates a procedure in which a 5G core network transmitsinformation for maintaining a MICO-mode UE in a connected state to aRAN.

In step 150, a UE 110 and an AMF 130 negotiate about whether to use aMICO mode during a registration procedure. The UE 110 may make a requestfor the MICO mode to the AMF 130 and may operate in the MICO mode onlywhen the AMF 130 allows the UE 110 to operate in the MICO mode.

The UE 110, which is allowed to operate in the MICO mode, enters theidle state after a predetermined time in step 155. In this state, the UE110 does not monitor a paging channel, and accordingly does not performa paging operation.

If the MICO-mode UE 110 has data to be transmitted, the UE 110 informs aNAS layer of the UE 110 that data communication is needed, and the NASlayer configures a service request message. In step 160, the UE 110transmits the service request message to the AMF 130 to activate a PDUsession required for data communication. The disclosure assumes that theUE 110 performed a PDU session establishment procedure before this step.

The AMF 130 determines that the received service request arrives fromthe MICO-mode UE 110 and then transmits a request for a procedure foractivating a PDU session to the SMF (not shown). After receiving a PDUsession activation response from the SMF (not shown), the AMF 130transmits a message for establishing a data radio bearer to a basestation 120 in step 165. In the disclosure, the message is called aninitial UE context setup, which corresponds to a message that the AMF130 transmits to the RAN node 120 in order to make a path for datatransmission to the UE 110. According to an embodiment of thedisclosure, the AMF 130 may insert information for assisting MICO-modeoperation of the UE 110 into the message. The information may includethe following information.

-   -   Indication indicating that the UE 110 is using the MICO mode    -   The time for which the UE 110 should maintain the connected        state in the MICO mode

The 5G RAN 120 receiving the message establishes a DRB with the UE 110through an RRC procedure in steps 170 and 175.

After succeeding in establishing the DRB, the 5G RAN 120 transmits aresponse to an initial UE context setup message to the AMF 130 in step180. The response may include an indication of the listed information(an indication indicating that the MICO mode is being used and the timefor which the connected state should be maintained) is applied.

According to an embodiment of the disclosure, the 5G RAN 120 may set atimer value for determining an inactive state of the RRC on the basis ofthe received information on the time for which the UE 110 shouldmaintain the connected state in the MICO mode in step 185. The 5G RAN120 internally sets an RRS inactive timer for determining RRC connectioninactivation of the UE 110. This may be used to determine that the RRCconnection is inactivated if there is no RRC operation of the UE 110 fora predetermined time, and after the timer expires, the 5G RAN 120performs an operation of releasing the radio resources allocated to theUE 110 and releasing the bearer. According to an embodiment of thedisclosure, the 5G RAN 120 may configure a larger value among the setRRC inactive timer and the received “time for which the UE 110 shouldmaintain the connected state in the MICO mode” (hereinafter, referred toas a MICO timer) as an RRC inactivity timer (that is, MAX{RRC inactivetimer, MICO timer}). According to another embodiment of the disclosure,the 5G RAN 120 may configure the received MICO timer as the RRCinactivity timer.

The 5G RAN 120 starts the configured timer from a time point at whichthe RRC operation of the UE 110 is not performed, and if the timerexpires, determines to release an RRC connection with the UE 110 and anN2 connection with the AMF 130 (the name of the interface between the 5GRAN 120 and the AMF 130 is N2) in step 190.

The 5G RAN 120 determining to release the connections transmits an N2release request to the AMF 130 in step 193, and the AMF 130 performs arelease procedure in step 195.

Embodiment 1-2 and FIG. 2

FIG. 2 illustrates a method by which a 5G core network storesinformation for maintaining a MICO-mode UE in a connected state andcontrols the release of a RAN connection.

In step 210, a UE 110 and an AMF 130 negotiate about whether to use aMICO mode during a registration procedure. The UE 110 may make a requestfor the MICO mode to the AMF 130 and may operate in the MICO mode onlywhen the AMF 130 allows the UE 110 to operate in the MICO mode.

The UE 110, which is allowed to operate in the MICO mode, enters theidle state after a predetermined time in step 215. In this state, the UE110 does not monitor a paging channel, and accordingly does not performa paging operation.

If the MICO-mode UE 110 has data to be transmitted, the UE 110 informs aNAS layer of the UE 110 that data communication is needed, and the NASlayer configures a service request message. The disclosure assumes thatthe UE 110 performed a PDU session establishment procedure before thisstep. In step 220, the UE 110 transmits the service request message tothe AMF 130 to activate a PDU session, which is required for datacommunication.

The AMF 130 determines that the received service request arrives fromthe MICO-mode UE 110 and then transmits a request for a procedure foractivating a PDU session to the SMF 140 in step 225. After receiving aPDU session activation response from the SMF 140, the AMF 130 transmitsa message for establishing a data radio bearer to a base station 120 instep 230. In the disclosure, the message is called an initial UE contextsetup, which corresponds to a message that the AMF 130 transmits to theRAN node 120 in order to make a path for data transmission to the UE110.

The 5G RAN 120 receiving the message establishes a data radio bearer(DRB) with the UE 110 through an RRC procedure in steps 235 and 240.

After succeeding in establishing the DRB, the 5G RAN 120 transmits aresponse to an initial UE context setup message to the AMF 130 in step245.

Thereafter, the UE 110 may start data communication in step 250.

According to an embodiment of the disclosure, the AMF 130 stores thetime for which the UE 110 should maintain the connected state in theMICO mode in the form of a context for the MICO-mode UE 110. Theinformation may be a value according to an internal policy of the AMF130, a value set for a data network name (DNN) used by the UE 110, or avalue according to a communication pattern indicating the time for whichthe corresponding UE 110 performs data communication or at which thedata communication is needed, which is configured by a 3rd-partyapplication server. In step 260, the AMF 130 knows that the UE 110 isusing the MICO mode, and accordingly, drives a timer (hereinafter,referred to as a MICO timer) for configuring the time for which the UE130 should maintain the connected state in the MICO mode.

If no RRC operation of the UE 110 is detected, the 5G RAN 120 drives theinternally configured RRC inactivity timer in step 255. If no RRCoperation of the UE 110 is detected when the RRC inactivity timerexpires, the 5G RAN 120 determines to release the RRC connection of theUE 110 and transmits an N2 release request to the AMF 130 in step 265.

The AMF 130 receiving the message identifies whether the MICO timer isdriven according to an embodiment of the disclosure. If the MICO timerdoes not expire, the AMF 130 rejects the N2 release request transmittedby the 5G RAN 120 in step 270. According to an additional embodiment,the AMF 130 may insert the remaining time of the MICO timer or a timevalue indicating how long the RAN 120 should wait into the rejectionmessage of the N2 release request or may provide an indicationindicating that the connection should be further maintained for thereason of rejection.

In step 275, the UE 110 having the non-released connection mayadditionally perform data transmission. If no RRC operation of the UE isdetected, the RAN 120 drives the RRC inactivity timer in step 280, andif the RRC inactivity timer expires, transmits an N2 release request tothe AMF 130 in step 290.

The AMF 130 receiving the message determines whether the MICO timer forthe corresponding UE expires in step 285. If the MICO timer expires, theAMF 130 performs an N2 release procedure in step 295.

Embodiment 1-3 and FIG. 3

FIG. 3 illustrates a method by which a 5G core network receives acommunication pattern for a corresponding UE from a 3rd-partyapplication server through an NEF and controls a MICO timer.

An application server 149 operated by the 3rd party may configure acommunication pattern of the corresponding UE 110, to which theapplication server provides a service, in a 5G network according to thecharacteristics of the service. The communication pattern may includethe following information.

-   -   Communication schedule of the UE 110: for example, Monday, 9:10        or 11:11 on November 11    -   Communication duration of the UE 110: Time for which the        connection is maintained if the UE initiates communication such        as 1 minute or 5 minutes    -   Communication delay of the UE 110: Traffic delay applied when        the AS provides a service to the UE, for example, 1 s or 800 ms

In step 310, the 3rd-party application server 149 transmits a requestfor configuring the communication pattern for the specific UE 110through a network exposure function (NEF) 147. The request messageincludes an identifier of the UE 110. In addition, the request messagemay include a DNN value, which is used when the UE 110 communicates withthe application server 149.

The NEF 147 receiving the request finds the requested AMF 130 servingthe UE 110 in step 320. Thereafter, according to an embodiment of thedisclosure, the NEF 147 transmits the requested communication pattern tothe AMF 130 serving the corresponding UE 110 in step 330. In thedisclosure, this is called a communication pattern provisioning requestfor convenience. According to an additional embodiment, the message isnot directly transmitted from the NEF 147 to the AMF 130, but the NEF147 may configure information of the UE 110 in user data management(UDM) (serving as an HSS in the past) and then the UDM may inform theAMF 130 of a context update of the UE 110, so that the communicationpattern may be transmitted to the AMF 130.

After receiving the communication pattern information, the AMF 130configures a MICO timer value for the UE 110 using the MICO mode in step340. Thereafter, the procedures illustrated in FIGS. 1 and 2 areperformed in step 350.

Embodiment 1-4 and FIG. 4

FIG. 4 illustrates a method by which a 5G core network receives acommunication pattern for a corresponding UE from a 3rd-partyapplication server through a PCF and controls a MICO timer.

An application server 149 operated by the 3rd party may configure acommunication pattern of the corresponding UE 110, to which theapplication server provides a service, in a 5G network according to thecharacteristics of the service. The communication pattern may includethe following information.

-   -   Communication schedule of the UE 110: for example, Monday, 9:10        or 11:11 on November 11    -   Communication duration of the UE 110: Time for which the        connection is maintained if the UE initiates communication, such        as 1 minute or 5 minutes    -   Communication delay of the UE 110: Traffic delay applied when        the AS provides a service to the UE, for example, 1 s or 800 ms.

In step 410, the 3rd-party application server 149 transmits a requestfor configuring the communication pattern for the specific UE 110through a network exposure function (NEF) 147. The request messageincludes an identifier of the UE 110. In addition, the request messagemay include a DNN value, which is used when the UE 110 communicates withthe application server 149.

The NEF 147 receiving the request transmits both the requestedidentifier of the UE 110 and the request to the PCF 141 in step 420.After authenticating the request, the PCF 141 finds the AMF 130 servingthe corresponding UE 110 in step 430. Thereafter, according to anembodiment of the disclosure, the PCF 141 transmits the requestedcommunication pattern to the AMF 130 serving the corresponding UE 110 instep 440. This may be included in policy information that the PCF 141transmits to the AMF 130.

After receiving the communication pattern information, the AMF 130configures a MICO timer vale for the UE 110 using the MICO mode in step450. Thereafter, the procedures illustrated in FIGS. 1 and 2 areperformed in step 460.

Embodiment 2

In the detailed description of embodiments of the disclosure, a radioaccess network will be mainly discussed on the basis of the 5G networkstandard defined by 3GPP, including a new RAN (NR) corresponding to acore network, and a packet core (5G system, 5G core network, or NG core(next-generation core)), but the main subject of the disclosure can beapplied with a slight change to other communication systems having asimilar technical background within the range that does not depart fromthe scope of the disclosure by the determination of a person skilled inthe art.

For the convenience of description, the disclosure uses terms and namesdefined in the 3rd-generation partnership project long-term evolution(3GPP LTE). However, the disclosure is not limited to the terms andnames, and may be equally applied to a system following anotherstandard.

Entities in the disclosure will be described below.

A user equipment (UE) is connected to a radio access network (RAN) andaccesses a device that performs a mobility management function of a 5Gcore network device. In the disclosure, the device is called an accessand mobility management function (AMF). This refers to a function or adevice that performs both access to the RAN and mobility management. TheAMF serves to forward a session-related message of the UE to a sessionmanagement function (SMF). The AMF is connected to the SMF, and the SMFis connected to a user plane function (UPF), allocate user planeresources to be provided to the UE, and establishes a tunnel fortransmitting data between a base station and the UPF. In the disclosure,the AMF may refer to a core network device providing mobility managementof the UE, that is, a device having another name that receives a NASmessage of the UE. For convenience, the device is called an accessmobility management function (AMF) in the disclosure.

4G is 4^(th)-generation mobile communication and includes radio accessnetwork technology called LTE and core network technology called evolvedpacket core (EPC). 5G is 5^(th)-generation mobile communication. Radioaccess network technology of 5G is called a next-generation RAN(NG-RAN), and core network technology is called a 5G system core.

A mobility restriction area is a set of area information including anallowed area in which a session is allowed to be established accordingto the location of the UE and thus data can be exchanged, a non-allowedarea in which a session for data communication cannot be established butonly control signaling is possible, and a forbidden area in which nomobile communication services are possible.

Embodiment 2-1 and FIG. 5

FIG. 5 illustrates a procedure in which a 5G core network performs adetermination to provide a specific service to a UE in a non-allowedarea, a paging method, and a response method of the UE, and FIG. 7illustrates a method by which a connection for a PDU session between theUE, a 5G RAN, and a UPF is established according to an embodiment of thedisclosure.

The 5G core network allocates mobility restriction area information tothe UE 110. This may be included in subscriber information or a policyfunction 141. The information is transmitted to the AMF 130, which theUE 110 accesses, and the AMF 130 transmits the information to the UE 110through a NAS procedure. Accordingly, the UE 110 and the AMF 130 havethe same mobility restriction area information.

If the UE 110 moves from the allowed area to the non-allowed area, theUE 110 may inform the AMF 130 that the UE 110 has entered thenon-allowed area through a registration update procedure. Accordingly,the AMF 130 may be made aware that the UE 110 is currently in thenon-allowed area. Similarly, if the UE 110 moves from the non-allowedarea to the allowed area, the UE 110 may inform the AMF 130 that the UE110 has entered the allowed area through the registration updateprocedure and that the session can be used.

Referring to FIG. 7, the UE 110 configures a session management NASmessage corresponding to a PDU session establishment request that makesa request for establishing a PDU session and transmits the sessionmanagement NAS message to the AMF 130 in step 710. After receiving themessage, the AMF 130 selects the SMF 140 capable of generating thecorresponding PDU session in step 720 and then transmits the messagereceived from the UE 110 to the SMF 140 in step 730. In step 740, theSMF 140 performs a PDU session establishment procedure with the UPF 145and the PCF 141 according to a request for establishing the PDU sessionfrom the UE 110 in step 740. In step 750, the SMF 140 informs the AMF130 of the PDU session establishment result. The message that the SMF140 transmits to the AMF 130 includes the PDU session establishmentmessage, which the SMF 140 transmits to the UE 110, in the form of asession management NAS message. According to an embodiment of thedisclosure, the message includes information indicating whether the PDUsession established in the UE 110 can override a service restriction.More specifically, the message may include an identifier indicatingwhether the PDU session established in the UE 110 can be used in thenon-allowed area. The SMF 140 may acquire the information from the PCF141. The PCF 141 may determine whether the corresponding PDU session canbe used in the non-allowed area according to an operator policy andtransmit the information to the SMF 140 when performing the PDU sessionestablishment procedure with the SMF 140. According to a more detailedembodiment, the SMF 140 may indicate whether the PDU session can be usedonly in the allowed area or can be used both in the allowed area and inthe non-allowed area through service restriction information indicatingwhether service restriction can be overridden. Alternatively, the SMFmay indicate only one thereof. The information may be indicated by anARP between a priority value or a QoS value. In another example, whetherthe PDU session can be used in the non-allowed area and the reasontherefor may be provided. The reason may include whether thecorresponding PDU session is for an emergency or public safety, whetherthe determination is by a local policy, or whether the PDU session isfor an operator-specific service. The AMF 130 receiving the informationstores a PDU session ID, which is the ID of a PDU session generated bythe corresponding SMF 140 and service restriction override informationthereof. According to another embodiment, if the AMF 130 storesinformation indicating that the corresponding PDU session can be used inthe non-allowed area, the AMF 130 performs PDU session activationwithout rejection when receiving the service request message that the UE110 transmits for the corresponding PDU session in the non-allowed area.

The AMF 130 transmits PDU session establishment accept, which is an SMNAS message received from the SMF 140, to the 5G RAN 120 in step 760,and accordingly the connection for the PDU session between the UE 110,the 5G RAN 120, and the UPF 145 is established. According to a detailedembodiment, the SMF 140 may insert information indicating whether thecorresponding PDU session is a PDU session which can be used in thenon-allowed area into the PDU session establishment accept messagetransmitted to the UE 110. After the UE 110 receives the message, if itis determined that the corresponding PDU session can be used in thenon-allowed area, the UE 110 may transmit a service request for thecorresponding PDU session after entering the non-allowed area in thefuture.

Referring to FIG. 5, it is assumed that the UE is in the non-allowedarea in the present embodiment.

If data traffic from the UPF 145 to the UE 110 is generated, the SMF 140receives information indicating that downlink data is generated in step511. The SMF 140 receiving the information transmits a downlink datanotification to the AMF 130 in order to wake up the UE 110 in step 513.The AMF 130 receiving the downlink data notification determines whetherpaging for the UE 110 is needed in step 510. In another example, when anSMS for the UE 110 arrives, the SMS interworking function 143 forproviding an SMS service may provide a notification indicating arrivalof the SMS to the AMF 130 or may directly transmit the SMS message tothe AMF 130. The AMF 130 receiving the downlink data notificationdetermines whether paging for the UE 110 is needed in step 520. Inaddition to the two examples, the AMF 130 also determines whether pagingfor the UE 110 is needed when another network service (for example, alocation-tracking service) makes a request to wake up the UE 110.

According to an embodiment of the disclosure, if the AMF 130 receives arequest for paging of the UE 110, such as a downlink data notificationmessage, the AMF 130 determines whether the UE 110 is currently in thenon-allowed area. The AMF 130, having determined that the UE 110 is inthe non-allowed area, determines whether to page the UE 110 according tothe following determination reference in step 540.

-   -   The AMF 130 identifies a data network name (DNN) for the        received downlink data notification in step 530. After        determining whether the DNN is a DNN for a voice DNN, a DNN for        an emergency service, or a DNN for public safety, the AMF 130        determines whether to page the UE 110 in step 540.    -   The AMF 130 identifies whether the entity transmitting the SMS        is a phone number for public safety, for example, 119 or 112, in        response to the request for the received SMS message, and        determines to page the UE 110 in step 540.    -   The AMF 130 identifies information on a network slice for the        received downlink data notification. If the corresponding        network slice is a network slice for emergency services, the AMF        130 determines to page the UE 110 in step 540. If the        corresponding network slice is a network slice for public        safety, the AMF 130 determines to page the UE 110.    -   If the received request is a request for tracking a location of        the UE 110 or if the AMF 130 detects that the request is related        to a location service that a service provider provides to the UE        110, the AMF 130 determines to page the UE 110 in step 540. The        location service that the service provider provides to the UE        110 may be a service such as a service for finding a missing UE.    -   When performing a PDU session establishment procedure for the ID        of the PDU session in which the downlink data notification is        received with the corresponding SMF 140, the AMF 130 determines        whether the corresponding PDU session can be paged in the        non-allowed area on the basis of received service restriction        override information. If the service restriction override        information includes information indicating that service is        allowed in the non-allowed area, the AMF 130 performs paging for        the corresponding downlink data notification in step 540.

According to an embodiment of the disclosure, the AMF 130 determiningthe paging determines the non-allowed area in which the UE 110 islocated in step 550. This may be a non-allowed area list which the AMF130 allocates to the UE 110. Alternatively, this may be a non-allowedarea list allocated to the UE 110 during the registration updateprocedure, performed when the UE 110 enters the non-allowed area.Alternatively, this may be the current location of the non-allowed areathat the UE 110 provides during the registration update procedure, whichis performed when the UE 110 enters the non-allowed area.

The AMF 130, determining the area to page the UE 110, transmits a pagingmessage to the 5G RAN node 120 in the corresponding area in step 560.

The 5G RAN 120 transmits the paging message for the corresponding UE 110to a cell managed by the 5G RAN according to the received paging requestin step 560.

According to an embodiment of the disclosure, when receiving paging, theUE 110 determines whether the location is the non-allowed area in step570. This may be identified on the basis of the non-allowed area listreceived from the AMF 130.

In step 580, the UE 110 may configure a service request message inresponse to paging (or configure the service request message byinserting an indication indicating that a session establishmentprocedure is needed into a registration update message). Whenconfiguring the service request message, the UE 110 may insert an ID ofthe PDU session to be used by the UE. According to an embodiment of thedisclosure, the UE 110 performs the following operation.

-   -   If the location at which to page the UE 110 is included in the        non-allowed area, the UE 110 does not insert the PDU session ID        into the service request message. This may mean that the UE 110        follows a PDU session established by the network without        indicating the PDU session to be used by the UE 110 (because of        the non-allowed area).    -   If the location at which to page the UE 110 is included in the        non-allowed area and if the PDU session used by the UE 110 is        for an emergency service, for public safety, or for a voice        call, the UE 110 inserts the corresponding PDU session ID into        the service request.    -   If the location at which to page the UE 110 is included in the        non-allowed area and if the PDU session used by the UE 110 is a        PDU session allowed by the SMF 140 to be used in the non-allowed        area, the UE 110 inserts the corresponding PDU session ID into        the service request.    -   If the location at which to page the UE 110 is included in the        non-allowed area and if the network slice used by the UE 110 is        a slice for public safety or emergency service, the UE 110        inserts the PDU session ID used by the corresponding network        slice into the service request.

After performing the determination operation, the UE 110 transmits theservice request to the AMF 130 in step 590. If the UE 110 inserts thePDU session ID for a service other than the service that the AMF 130determines to page into the service request, the AMF 130 does notactivate the PDU session for the corresponding PDU session ID. This maybe indicated by the service accept message transmitted to the UE 110.

Meanwhile, according to an embodiment of the disclosure, if the UE 110makes a registration request in the non-allowed area, the UE 110 cannotuse the PDU session in the non-allowed area, so the AMF 130 makes arequest for deactivating the PDU session to the SMF 140 in order todeactivate the PDU session used by the UE 110. The request fordeactivating the PDU session may mean that the AMF 130 may transmitinformation indicating current entry of the UE 110 into the non-allowedarea to the SMF 140 without making an explicit request for deactivatingthe PDU session and the SMF 140 receiving the information determineswhether to deactivate the PDU session on the basis of the information.According to a detailed embodiment of the disclosure, if the AMF 130receives a registration request performed as the UE 110 enters thenon-allowed area, the AMF 130 transmits a PDU session deactivationmessage including a cause value indicating that the UE 110 has enteredthe non-allowed area to the SMF 140. Alternatively, the AMF 130transmits information indicating whether the UE 110 enters thenon-allowed area, made known through the registration procedure, to theSMF 140 as UE reachability state information, and the SMF 140 maydetermine PDU session deactivation on the basis of the information.According to an embodiment of the disclosure, the SMF 140 receiving theinformation may determine whether the PDU session that the SMF 140provides to the UE 110 is a PDU session that should be provided in thenon-allowed area, and may transmit a response indicating rejection ofPDU session deactivation along with a cause value, indicating thatservice is possible in the non-allowed area, to the AMF 130. Afterreceiving the cause value and the response, the AMF 130 may determinethat the corresponding PDU session can be serviced in the non-allowedarea. After storing it, the AMF 130 determines that the PDU session canbe serviced in the non-allowed area when the corresponding SMF 140receives a downlink data notification and makes a request for paging theUE 110 to the AMF 130 in the future, and then pages the UE 110.Alternatively, the SMF 140 may determine that the PDU session which theSMF provides to the UE 110 is a PDU session that should be serviced inthe non-allowed area, does not deactivate the PDU session, and transmitno response to the AMF 130. If downlink data for the corresponding PDUsession is generated in the future, the SMF 140 provides the downlinkdata notification to the AMF 130.

Embodiment 2-2 and FIG. 6

FIG. 6 illustrates a method by which a 5G network processes a sessionestablishment request message transmitted by a UE in the non-allowedarea and a method of activating a session by the UE in the future.

If the UE 110 receives information about the non-allowed area from the5G network, the UE 110 may determine whether the UE 110 is to make arequest for a message for establishing a session. However, if the UE 110has not yet received the information about the non-allowed area, the UEmay transmit a message for establishing a session.

According to an embodiment of the disclosure, it is assumed that the UE110 is not aware of whether the current location of the UE belongs tothe non-allowed area in step 610, and it is assumed that the AMF 130 isaware that the current location of the UE 110 belongs to the non-allowedarea.

Non-reception of the non-allowed area by the UE 110 may mean that the UE110 has not yet performed the registration procedure. The UE 110 maytransmit a request message for establishing the session while performingthe registration procedure. According to the present embodiment, the UE110 also transmits the request message for establishing the sessionwhile performing the registration procedure, which is a proposal for thecase in which the AMF 130 determines that the area in which the UE 110is located is the non-allowed area.

In step 615, the UE 110 transmits a registration request to the AMF 130to access the 5G network. In order to indicate the situation in whichthere is no pre-allocated non-allowed area, the message is named aninitial registration request for convenience. The initial registrationrequest is not necessarily an initially transmitted registrationrequest, but corresponds to a registration request transmitted by the UE110, the current location of which is not identified to be thenon-allowed area or not. The UE 110 inserts an SM message for PDUsession establishment into the message and transmits the message. ThePDU session establishment message is a message that makes a request forestablishing a PDU session to be used by the UE 110. The UE 110allocates an ID of the PDU session to be used by the UE and inserts theID into the message. This is information that can be understood by theAMF 130.

After receiving the message, the AMF 130 identifies the ID of the UE 110and then acquires the context of the UE 110 in step 620. If the AMFalready has the context of the UE 110, the AMF identifies the context.

In order to determine whether the UE 110 transmitting the message is inthe non-allowed area, the AMF 130 compares area information included inthe registration request message transmitted by the UE 110 withnon-allowed area information of the UE 110 included in the context ofthe UE 110 in step 625. Further, the AMF 130 determines whether themessage includes an SM message.

According to an embodiment of the disclosure, the AMF 130, identifyingthat the UE 110 is located in the non-allowed area to transmit theregistration request and that the message includes the SM message, maydetermine the following operation in step 630.

-   -   The AMF 130 determines whether the PDU session establishment        request transmitted by the UE 110 can be processed in the        non-allowed area. This may be a determination of whether a data        network name (DNN) is for an emergency service or a regulatory        prioritized service on the basis of the data network name (DNN)        for the PDU session establishment request. If the DNN is for the        emergency or regulatory prioritized service, it is determined to        establish the PDU session. Alternatively, if the registration        type of the UE 110 is an emergency, it is determined that the UE        110 can establish the PDU session even in the non-allowed area.        If the above condition is not satisfied, the AMF 130 determines        that the UE 110 cannot establish the PDU session and thus may        not perform a procedure for an SM request. At this time (when        the PDU session is not established), the AMF 130 may perform two        operations. For example, the AMF 130 may identify policy or        subscription information of the UE 110, and if it is identified        that the corresponding UE 110 is a UE which is not able to        perform registration without PDU session establishment, the UE        110 cannot establish the PDU session in the current location, so        the AMF 130 may reject the registration request. Accordingly,        the AMF 130 may transmit the registration rejection to the UE,        in which case the registration rejection may include a cause        indicating the non-allowed area, a cause indicating service area        restriction, or a cause indicating PDU session establishment        failure. In another operation, the AMF 130 may identify policy        or subscription information of the UE 110, and if it is        identified that the corresponding UE 110 is a UE capable of        performing registration without PDU session establishment, may        complete the registration procedure even though the UE 110        cannot establish the PDU session at the current location.        Accordingly, the AMF 130 performs a procedure for accepting the        registration request transmitted by the UE 110 and transmits a        registration acceptance message to the UE 110. At this time, the        AMF 130 may include a cause value indicating that the PDU        session establishment requested by the UE 110 is rejected. The        cause value may be a value indicating the non-allowed area or a        value indicating service area restriction.    -   In a more advanced method according to an embodiment of the        disclosure, if the UE 110 makes a request for establishing the        PDU session in the non-allowed area, the AMF 130 may establish a        PDU session that can be used by the UE 110 on the side of the        core network but not allocate radio resources for the        corresponding PDU session to the UE 110 so as to limit the use        of the PDU session of the UE 110. This causes the SMF 140 and        the UPF 145 to establish the PDU session for the UE 110 and to        generate a context but results in non-establishment of the user        plane connection for the PDU session between the base station        120 and the UE 110 and between the base station 120 and the UPF        145. In other words, although the UE 110 establishes the PDU        session, an idle state results (user plane connection is        inactive). Accordingly, there is an effect of reducing time and        signaling as the UE 110 activates the existing PDU session to        use the same without again performing the PDU session        establishment procedure when the UE 110 enters the allowed area        in the future.

The AMF 130, determining to establish the PDU session only on the sideof the core network, selects the SMF 140 to which the SM messagereceived from the UE 110 is transmitted in step 635.

After selecting the SMF 140, the AMF 130 transmits the SM messagereceived from the UE 110 to the corresponding SMF 140 in step 640. Themessage includes a PDU session establishment request.

The SMF 140 performs a PDU session setup procedure with the UPF 145 andthe PCF 141 according to the received SM message in step 645.

The SMF 140 transmits ACK to the AMF 130 to inform the AMF that the PDUsession is established on the side of the core network in step 650.

According to an embodiment of the disclosure, the AMF 130 determinesthat the ACK is ACK of the SM message of the UE 110 in the non-allowedarea in step 655.

According to an embodiment of the disclosure, the AMF 130 determines notto establish the connection (N3 connection) between the base station 120and the UPF 145 and radio resources of the UE 110 according to thedetermination in the procedure in step 660.

The AMF 130 transmits a registration acceptance message to the UE 110 instep 665. According to an embodiment of the disclosure, the AMF 130 mayindicate the cause of failure in the SM request of the UE 110 throughthe message. This may have a form such as session establishment requestfailure—cause: non-allowed area. Further, the AMF 130 inserts an ID ofthe PDU session, established on the side of the core network, into themessage. The ID may be a PDU session ID included in the SM messagepiggybacking on the registration request by the UE 110.

The UE 110 may provide notification of reception of the registrationacceptance message in step 670.

The UE 110 and the AMF have established the current PDU session butconsider that a user plane connection is inactive in step 675.

The AMF 130 informs the SMF 140 that the user plane connection of the UE110 is inactive, and thus the SMF 140 does not wait for the connectionbetween the UE 110 and the base station 120. The SMF 140 considers theUE 110 to be in an idle state.

According to an embodiment of the disclosure, if the UE 110 enters theallowed area in the future in step 680, the UE 110 may activate the userplane connection for the PDU session established on the side of the corenetwork through a request in step 695. In order to provide notificationof entry into the allowed area before step 695, the UE 110 might performa registration update procedure in step 685. In order to activate theuser plane connection for the PDU session, the UE 110 transmits aservice request message including the ID of the corresponding PDUsession to the AMF 130 in step 690. The AMF 130 receiving the servicerequest message makes a request for activating the user plane connectionto the SMF 140 associated with the corresponding PDU session ID so as toallow the UE 110 to transmit and receive data through the PDU session instep 695.

In a situation according to another embodiment of the disclosure, if theUE 110 escapes the registration area allocated by the AMF 130, the UE110 transmits a registration request to the AMF 130 to perform aregistration area update procedure in step 615. When transmitting theregistration request, the UE 110 may transmit an indication related toPDU session reactivation (for example, a PDU session ID) in order toreactivate the PDU session established by the UE. If the UE 110 enters anon-allowed area, the UE 110 should not transmit the PDU sessionreactivation indication. However, if the UE 110 is not aware of entryinto a non-allowed area, the UE 110 may transmit the PDU sessionreactivation indication through the registration request. That is, theembodiment is implemented when the registration update procedure isperformed due to movement of the UE 110 and when the corresponding UE110 enters a non-allowed area as well as when the UE 110 performs theinitial registration procedure.

After receiving the message, the AMF 130 identifies the ID of the UE 110and then acquires a context of the UE 110 in step 620. If the AMFalready has the context of the UE 110, the AMF identifies the context.

In order to determine whether the UE 110 transmitting the message is ina non-allowed area, the AMF 130 compares area information included inthe registration request message transmitted by the UE 110 withnon-allowed area information of the UE 110 included in the context ofthe UE 110 in step 625. Further, the AMF 130 identifies whether themessage includes a PDU session reactivation indication (for example, oneof a PDU session ID, a flag, or an identifier indicating reactivation ofall PDU sessions). The AMF 130, identifying that the UE 110 is locatedin the non-allowed area to transmit the registration request and thatthe message includes an identifier for PDU session reactivation, maydetermine the following operation in step 630.

-   -   The AMF 130 determines whether the PDU session reactivation        request transmitted by the UE 110 can be processed in the        non-allowed area. This may be a determination of whether the        corresponding data network name (DNN) is for an emergency        service or a regulatory prioritized service after the DNN of the        corresponding PDU session is identified on the basis of the ID        of the PDU session for the PDU session reactivation request. If        the DNN is for the emergency or regulatory prioritized service,        it is determined to reactivate the PDU session. Alternatively,        if the registration type of the UE 110 is an emergency, it may        be determined that the UE 110 can reactivate the PDU session        even in the non-allowed area. The AMF 130 determining that the        PDU session can be reactivated transmits an Nil message that        makes a request for reactivating the PDU session to the SMF 140        to prompt the PDU session reactivation. If the above conditions        are not satisfied, the AMF 130 determines that the UE 110 cannot        reactivate the PDU session and thus may not perform a procedure        for the PDU session with the SMF. As described above, if the        procedure for the PDU session reactivation is not performed, the        AMF 130 may perform two operations. First, the AMF identifies        policy or subscription information of the UE 110 and identifies        that the corresponding UE 110 is a UE that is not capable of        maintaining registration without a PDU session. Then, the AMF        identifies a PDU session context of the corresponding UE 110 so        as to determine whether the corresponding PDU session is        released. The PDU session context may be session management        message information for the release of the PDU session that is        pended by the AMF 130 without waking up the UE 110 by the AMF        130 since the UE 110 is in the idle state and the SMF 140 has        transmitted information indicating the release of the PDU        session for the UE 110 to the AMF. After identifying that the        PDU session that the UE 110 desires to reactivate has already        been released and that the PDU session cannot be established in        the non-allowed area, which is the current location, if it is        determined that the UE 110 cannot maintain the registration        state without at least one PDU session, the AMF 130 may reject        the registration request. Accordingly, the AMF 130 may transmit        the registration rejection to the UE 110, in which case the        registration rejection may include a cause indicating the        non-allowed area, a cause indicating service area restriction,        or a cause indicating PDU session reactivation failure.        Alternatively, the registration rejection may include a cause        indicating that registration cannot be maintained without a PDU        session, such as failure of registration because no PDU session        exist. Further, the AMF 130 may indicate that the PDU session is        released while transmitting the cause including the status of        the PDU session used/established by the UE 110.

In another operation, the AMF 130 identifies policy or subscriptioninformation of the UE 110 and identifies that the corresponding UE 110is a UE capable of performing registration without PDU sessionestablishment. Further, if the AMF 130 receives a notificationindicating that there is no PDU session that can be currently used bythe UE 110 and that all PDU sessions that the UE 110 has established arereleased from the SMF 140, the AMF 130 may complete the registrationprocedure even though the UE 110 cannot reactivate the PDU session atthe current location and all the PDU sessions are currently released.Accordingly, the AMF 130 performs a procedure for accepting theregistration request transmitted by the UE 110 and transmits aregistration acceptance message to the UE 110. At this time, the AMF 130may include a cause value indicating that the PDU session reactivationrequested by the UE 110 is rejected. The cause value may include a valueindicating the non-allowed area, a value indicating service arearestriction, or a value indicating PDU session reactivation failure.Further, the AMF 130 may include the status of the PDU sessionused/established by the UE 110 while transmitting the cause, and mayprovide notification that the corresponding PDU session is released.

FIG. 8 is a block diagram illustrating a base station according to anembodiment of the disclosure.

Referring to FIG. 8, a base station 120 according to an embodiment ofthe disclosure may include a transceiver 810 and a controller 820 forcontrolling the overall operation of the base station 120. Thetransceiver 810 may include a transmitter 813 and a receiver 815. Thebase station 120 may further include a storage unit 830.

The controller 820 of the base station 120 controls the base station 120to perform one operation in the above-described embodiments. Forexample, the controller 820 of the base station 120 may perform controlto receive a first message including information for maintaining theMICO-mode UE 110 in the connected state from the AMF 130, determinewhether to release the connection of the MICO-mode UE 110 on the basisof the information, and if it is determined to release the connection ofthe MICO-mode UE 110, transmit a second message that makes a request forreleasing the connection from the AMF 130. The controller 820 mayperform control to configure a timer for a connection maintenance timeof the MICO-mode UE 110 on the basis of the information, and if thetimer expires, transmit the second message, which makes a request forreleasing the connection to the AMF 130.

The transceiver 810 of the base station 120 may transmit and receive asignal according to one operation in the above-described embodiments.

Meanwhile, the controller 820 and the transceiver 810 do not have to beimplemented as separate modules but may be implemented as one elementsuch as a single chip. The controller 820 and the transceiver 810 may beelectrically connected.

For example, the controller 820 may be a circuit, anapplication-specific circuit, or at least one processor. Operation ofthe base station may be implemented as a memory device (the storage unit830) storing the corresponding program code is included in apredetermined element within the base station 120. That is, thecontroller 820 may perform the operations by reading and executing theprogram code stored in the memory device through a processor or acentral processing unit (CPU).

FIG. 9 is a block diagram illustrating an AMF according to an embodimentof the disclosure.

Referring to FIG. 9, an AMF 130 according to an embodiment of thedisclosure may include a transceiver 910 and a controller 920 forcontrolling the overall operation of the AMF 130. The transceiver 910may include a transmitter 913 and a receiver 915. The AMF 130 mayfurther include a storage unit 930.

The controller 920 of the AMF 130 controls the AMF 130 to perform oneoperation in the above-described embodiments. For example, thecontroller 920 of the AMF 130 may perform control to transmit a firstmessage including information for maintaining the MICO-mode UE 110 inthe connected state to the base station 120, and if it is determined torelease the connection of the MICO-mode UE 110 on the basis of theinformation, receive a second message that makes a request for releasingthe connection from the base station 120. When a timer for a connectionmaintenance time of the MICO-mode UE 110, configured on the basis of theinformation, expires, the controller 920 may receive the second message,which makes a request for releasing the connection from the base station120.

The transceiver 910 of the AMF 130 may transmit and receive a signalaccording to one operation in the above-described embodiments.

Meanwhile, the controller 920 and the transceiver 910 do not have to beimplemented as separate modules but may be implemented as one element,such as a single chip. The controller 920 and the transceiver 910 may beelectrically connected.

For example, the controller 920 may be a circuit, anapplication-specific circuit, or at least one processor. Operations ofthe AMF 130 may be implemented as a memory device (the storage unit 930)storing the corresponding program code is included in a predeterminedelement within the UE. That is, the controller 920 may perform theoperations by reading and executing the program code stored in thememory device through a processor or a central processing unit (CPU).

Other network entities (for example, the UE 110, the SMF 140, the UPF145, the AS 149, the PCF 141, and the NEF 147) may include a transceiverand a controller for controlling the overall operation of the networkentities. The transceiver may include a transmitter and a receiver, andthe network entities may further include a storage unit. The controllercontrols the network entities to perform one operation in theabove-described embodiments. The controller and the transceiver do nothave to be implemented as separate modules but may be implemented as oneelement, such as a single chip, and the controller and the transceivermay be electrically connected.

Meanwhile, the embodiments of the disclosure disclosed in thespecification and the drawings have been presented to easily explaintechnical contents of the disclosure and help comprehension of thedisclosure, and do not limit the scope of the disclosure. That is, it isobvious to those skilled in the art to which the disclosure belongs thatdifferent modifications can be achieved based on the technical spirit ofthe disclosure. Further, if necessary, the above respective embodimentsmay be employed in combination. For example, the base station and the UEmay operate on the basis of a combination of portions of embodiment 1and embodiment 2 of the disclosure. Although the embodiments have beenpresented on the basis of LTE/LTE-A systems, other modified examplesbased on the technical idea of the embodiments can be applied to othersystems such as 5G and NR systems.

The invention claimed is:
 1. A method performed by a base station in awireless communication system, the method comprising: receiving, from anaccess and mobility management function (AMF), a first message includingfirst information indicating a mobile initiated communication only(MICO) mode is used by a terminal, wherein the terminal in the MICO modedoes not listen to a paging from the AMF while the terminal is in anidle state; identifying whether the first message further includessecond information on a time to maintain the terminal in the MICO modein a connection state; and maintaining the terminal in the connectedstate for the time to deliver downlink traffic to the terminal based onthe second information, in case that the first message further includesthe second information.
 2. The method of claim 1, further comprising:determining whether the time expires; and in case that the time expires,transmitting, to the AMF, a second message for releasing a connectionbetween the base station and the AMF.
 3. The method of claim 1, whereinthe second information on the time indicates a minimum time that thebase station keeps the terminal in the connected state regardless ofinactivity.
 4. The method of claim 1, wherein the second information onthe time is determined based on information for identifying a time forwhich the terminal stays reachable, and wherein the information istransmitted from a user data management (UDM) to the AMF.
 5. A methodperformed by an access and mobility management function (AMF) in awireless communication system, the method comprising: transmitting, to abase station, a first message including first information indicating amobile initiated communication only (MICO) mode is used by a terminaland second information on a time to maintain the terminal in the MICOmode in a connection state, wherein the terminal in the MICO mode doesnot listen to a paging from the AMF while the terminal is in an idlestate; and maintaining a connection between the base station and the AMFfor the time to deliver downlink traffic to the terminal.
 6. The methodof claim 5, further comprising: in case that the time expires,receiving, from the base station, a second message for releasing theconnection between the base station and the AMF.
 7. The method of claim5, wherein the second information on the time indicates a minimum timethat the base station keeps the terminal in the connected stateregardless of inactivity.
 8. The method of claim 5, further comprising:receiving, from a user data management (UDM) information for identifyinga time for which the terminal stays reachable; and determining thesecond information on the time based on the information received fromthe UDM, wherein the determined second information on the time isincluded in the first message.
 9. A base station in a wirelesscommunication system, the base station comprising: a transceiver; and acontroller configured to: control the transceiver to receive, from anaccess and mobility management function (AMF), a first message includingfirst information indicating a mobile initiated communication only(MICO) mode is used by a terminal, wherein the terminal in the MICO modedoes not listen to a paging from the AMF while the terminal is in anidle state, identify whether the first message further includes secondinformation on a time to maintain the terminal in the MICO mode in aconnection state, and maintain the terminal in the connected state forthe time to deliver downlink traffic to the terminal based on the secondinformation, in case that the first message further includes the secondinformation.
 10. The base station of claim 9, wherein the controller isfurther configured to: determine whether the time expires, and in casethat the time expires, control the transceiver to transmit, to the AMF,a second message for releasing a connection between the base station andthe AMF.
 11. The base station of claim 9, wherein the second informationon the time indicates a minimum time that the base station keeps theterminal in the connected state regardless of inactivity.
 12. The basestation of claim 9, wherein the second information on the time isdetermined based on information for identifying a time for which theterminal stays reachable, and wherein the information is transmittedfrom a user data management (UDM) to the AMF.
 13. An access and mobilitymanagement function (AMF) comprising: a transceiver; and a controllerconfigured to: control the transceiver to transmit, to a base station, afirst message including first information indicating a mobile initiatedcommunication only (MICO) mode is used by a terminal and secondinformation on a time to maintain the terminal in the MICO mode in aconnection state, wherein the terminal in the MICO mode does not listento a paging from the AMF while the terminal is in an idle state, andmaintain a connection between the base station and the AMF for the timeto deliver downlink traffic to the terminal.
 14. The AMF of claim 13,wherein the second information on the time indicates a minimum time thatthe base station keeps the terminal in the connected state regardless ofinactivity, and wherein the controller is further configured to controlthe transceiver to receive, in case that the time expires, a secondmessage for releasing the connection between the base station and theAMF.
 15. The AMF of claim 13, wherein the controller is furtherconfigured to control the transceiver to receive, from a user datamanagement (UDM) information for identifying a time for which theterminal stays reachable, and determine the second information on thetime based on the information received from the UDM, and wherein thedetermined second information on the time is included in the firstmessage.